This invention relates to an automated apparatus and method for processing a part, such as the root of a turbine blade.
The conventional turbine blade has a main blade body which is typically encased within a rectangular block of lead so that only the root projects outwardly thereof for subsequent processing. This root, which typically has a dove-tail shaped cross section, is at present machined in a manner which results in a plurality of sharp corners or edges where the side surfaces of the root meet the end surface. The blade or part is sent to a first working station where an operator manually applies a tool to each of the edges of the root to remove excess material and create a chamfer. The chamfered part is then sent to a buffing station typically including a number of separate buffing wheels, and the blade is then progressively advanced from one wheel to another to effectively round off all corners along the respective chamfered edges. The overall operation as briefly described above requires significant manual control and supervision, and in particular is not adapted for fully automated handling. Further, the machinery is bulky, complex and requires a large amount of floor space.
It is an object of this invention to provide a relatively compact machining or finishing cell for deburring and/or chamfering the root edges of a turbine blade, which can be positioned on a floor with a small footprint, and which can be wholly automated so as to effectively permit essentially automatic 24-hour operation without any significant manual control or supervision, other than for certain checking and replenishment functions.
Generally, the machining cell according to the invention is an enclosed structure and defines therein an enclosed work area within which a robot is disposed and functions to pick up and transport a part, such as a blade package, between various working stations also located within the cell. More specifically, the part is fed into the cell by a supply conveyor which transports the part to a part orienter station located inside the cell where the part is checked for type and proper orientation prior to being picked up or grasped by the robot. If the wrong part has been loaded onto the supply conveyor, or if the part is improperly oriented for processing, then the part is rejected, and a new part is moved into the part orienter station. If the part is the correct part and is properly oriented, as determined by the part orienter station, then the robot picks up the part and transports same to a deburring or cutting station.
The deburring station includes a turret which supports thereon a pair of diametrically opposed tool heads, each including a hard, drill-like cutting tool or burr rotated by a motor. The turret is rotatable to effectively position one tool head in an active cutting position and the opposite head in an inactive position. The robot transports the part and manipulates same along a predefined path to bring the part into engagement with the active cutting tool to remove excess material from the root of the blade package or part. The tool heads are mounted on the turret so that the respective tools thereof are movable or float. As such, the robot need not be taught or programmed to move the part along an exact path for proper processing, since the floating tool is biased in a manner so that same will follow the root profile and maintain engagement therewith.
The deburring station cooperates with a tool supply and replacement device which serves to remove broken or worn tools from the inactive tool head and replace same with new tools stored in a supply cartridge. Prior to positioning the part for engagement with the active tool as discussed above, a sensor arrangement provided adjacent the active tool senses for a broken, bent or improperly oriented tool, and if the tool is unsatisfactory in any of these respects, then further advancement of the robot is stopped, the active tool head is rotated into an inactive position (which rotates the inactive tool head into the active position for processing of the part) and the defective or improperly positioned tool is removed and replaced by the tool supply and replacement device. The condition of the active tool is also checked subsequent to processing a part, and if the tool is in an unsatisfactory condition, then same is replaced and the part just processed with the broken or improperly oriented tool is rejected.
After processing of the part at the deburring station, the robot then transports the part to a brushing or polishing station for finishing. The brushing station is also located within the cell and includes one or more brushing wheels defined by filaments containing an abrasive material. The robot moves the part so that all edges of the root are appropriately subjected to the abrasive action of the wheel for a predetermined time to finish or round the edges thereof. The brushing station incorporates a wear compensation mechanism which operates to maintain a substantially constant contact point and a substantially constant contact velocity between the part and the brushing wheel as same wears and decreases in radius. The finished part is then transported by the robot to a discharge conveyor which feeds the finished part outside of the cell.
The functioning of the various stations within the cell, including the robot and conveyors, is controlled via a logic type controller and by software which enables a substantially entirely automated operation. A control unit including a touch-sensitive video screen is also provided outside the cell for providing operator control and for monitoring of the system. This control unit is swingably mounted for movement to various locations around the cell for convenience in use.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.